Due to their relatively simple implementation and low cost in the application of intermediate speed and resolution, pipeline analog-to-digital converters (ADC) are found in various applications including image sensors, communications equipment, and televisions. Because of the pipeline ADC's piecewise linear nature, missing codes (i.e., errors in the digital output) caused by capacitor mismatch, limited operational-amplifier (OP-AMP) gain, settling errors and inaccurate reference voltages are more pronounced. As a result, missing codes (especially those found in the earlier stages of a pipeline ADC) could significantly degrade the digital output, such as the visual quality of an image produced by an image sensor.
Degradation in the visual quality of an image or missing codes are typically reduced with calibration circuits included in the pipeline ADC. However, calibration circuits take up space on the image sensor die and increase the power consumption of the image sensor.